Robot gripper

ABSTRACT

Provided is a robot gripper. The robot gripper comprises: at least two finger units which symmetrically face each other; finger tips which are provided at the terminal ends of the finger units and linked with the operation of the finger units; and a driving unit connected to the finger units so as to operate the finger units. When the finger units are operated, the finger tips pinch-grip an object by moving toward an inner area, which at least two of the finger units form by facing each other, while adapting to conflicts with constraints of the external environment. A force applied to the finger tips in order to enable the pinch grip can act in a direction that raises the object while being applied toward the inner area, or act in a direction lowering the object while being applied toward the inner area.

TECHNICAL FIELD

The present invention relates to a robot gripper, and more particularly,to a robot gripper capable of adapting to environmental constraints.

BACKGROUND ART

The most representative gripper is a gripper developed by C. M.Gosselin, and various grippers developed so far follow advantages of thegripper developed by C. M. Gosselin.

The gripper developed by C. M. Gosselin implements pinch grip andobject-adaptive grasp by using one driver per finger module. In detail,the gripper may grasp an object as a finger adapts to a shape of anobject when the gripper grasps a relatively large object, and may pinchan object as a fingertip maintains a perpendicular angle by aparallelogram mechanism when the gripper pinches a relatively smallobject.

In this case, since most objects are placed on a table, there areenvironmental constraints, and when a small object is pinched, acollision and contact between a table surface and a fingertip mayfrequently occur.

However, according to the related art, considerations on theenvironmental constraints that actually occur have been rarely made in aprocess of developing a gripper.

DISCLOSURE Technical Problem

One technical object of the present invention is to provide a robotgripper capable of adapting to environmental constraints.

Another technical object of the present invention is to provide a robotgripper having strong pinch grip ability.

Still another technical object of the present invention is to provide anunderactuated robot gripper operated by one driver.

Yet another technical object of the present invention is to provide arobot gripper capable of performing object-adaptive grasp.

Technical objects of the present invention are not limited to theabove-described technical objects.

Technical Solution

To achieve the technical objects described above, the present inventionprovides a robot gripper.

According to one embodiment, the robot gripper includes: at least twofinger units symmetrically facing each other; a fingertip provided at aterminal end of the finger unit, and interworking with an operation ofthe finger unit; and a driving unit connected to the finger unit tooperate the finger unit, wherein, when the finger unit is operated, thefingertip pinch-grips an object by moving toward an inner area, which isformed as the at least two finger units face each other, while adaptingto a conflict with a constraint of an external environment, and a forceapplied to the fingertip to enable the pinch grip acts in a direction ofraising the object upward while acting toward the inner area, or acts ina direction of lowering the object downward while acting toward theinner area.

According to one embodiment, the finger unit may include a four-bar linkdevice, and a vector direction of the force applied to the fingertip maybe determined according to a length relation of links that constitutesides of the four-bar link device, respectively.

According to one embodiment, the finger unit may further include aconnection link, the connection link may connect the four-bar linkdevice to the fingertip, and the four-bar link device may include: aninput link having one longitudinal end connected to the driving unit; anoutput link facing the input link, and having one longitudinal endconnected to one longitudinal end of the connection link; anintermediate link connected between an opposite longitudinal end of theinput link and an opposite longitudinal end of the output link; and aframe link connected between the one longitudinal end of the output linkand the one longitudinal end of the input link.

According to one embodiment, a length relation of the input link, theintermediate link, and the output link may be defined according tovector directions of forces generated when an opposite longitudinal endof the connection link makes contact with any three points on ahorizontal plane, and, based on the defined length relation, a forceacting in the direction of raising the object upward while acting towardthe inner area may be applied to the fingertip, or a force acting in thedirection of lowering the object downward while acting toward the innerarea may be applied to the fingertip.

According to one embodiment, while the output link has a relativelyshorter length than the input link and the intermediate link, when theinput link has a relatively shorter length than the intermediate link,the force applied to the fingertip may act in the direction of raisingthe object upward while acting toward the inner area.

According to one embodiment, while the output link has a relativelyshorter length than the input link and the intermediate link, when theinput link has a relatively longer length than the intermediate link,the force applied to the fingertip may act in the direction of loweringthe object downward while acting toward the inner area.

According to one embodiment, an angle formed between the connection linkand the output link, which is set when the force applied to thefingertip acts in the direction of raising the object upward whileacting toward the inner area, may be relatively greater than an angleformed between the connection link and the output link, which is setwhen the force applied to the fingertip acts in the direction oflowering the object downward while acting toward the inner area.

According to one embodiment, the finger unit may further include aparallelogrammic link device, and the parallelogrammic link device maybe coupled to the four-bar link device and the connection link tomaintain an installation angle of the fingertip, and may be dependent onan operation of the four-bar link device.

According to one embodiment, the finger unit may further include astopper, and the stopper may be formed between the output link and theframe link, and configured to restrain a rotation of the output link ina direction of increasing an angle formed between the output link andthe frame link.

According to one embodiment, the finger unit may further include anelastic member, and the elastic member may be formed between the outputlink and the frame link, elastically deformed in a case where aninclination of the output link is changed to increase an angle formedbetween the output link and the frame link when the driving unit isdriven, and configured to recover the inclination of the output linkinto an initial state through an elastic restoring force so that theangle formed between the output link and the frame link forms aninitially set angle again when the driving unit is not driven.

According to one embodiment, the at least two finger units may beunderactuated by the driving unit.

According to one embodiment, the driving unit may include: one motor;one worm gear rotated by the one motor; and worm wheels provided in anumber corresponding to the at least two finger units so as to beconnected to the at least two finger units, respectively, and engagedwith the one worm gear so as to be rotated.

Advantageous Effects

According to an embodiment of the present invention, the robot gripperincludes: at least two finger units symmetrically facing each other; afingertip provided at a terminal end of the finger unit, andinterworking with an operation of the finger unit; and a driving unitconnected to the finger unit to operate the finger unit, wherein, whenthe finger unit is operated, the fingertip pinch-grips an object bymoving toward an inner area, which is formed as the at least two fingerunits face each other, while adapting to a conflict with a constraint ofan external environment, and a force applied to the fingertip to enablethe pinch grip acts in a direction of raising the object upward whileacting toward the inner area, or acts in a direction of lowering theobject downward while acting toward the inner area.

Accordingly, a robot gripper capable of adapting to environmentalconstraints, which is a robot gripper configured such that a fingertipflexibly slides on a table surface to pinch-grip an object even when thefingertip collides with table surfaces having various inclinations andon which the object is placed, can be provided.

In addition, according to an embodiment of the present invention, arobot gripper having strong pinch grip ability can be provided.

In addition, according to an embodiment of the present invention, anunderactuated robot gripper in which at least two finger units areoperated by a driving unit including one motor can be provided.

In addition, according to an embodiment of the present invention, anelastic member may be provided between an output link and a frame link,so that a robot gripper capable of adaptive-grasping an object throughelasticity and an elastic restoring force of the elastic member when arelatively large object is grasped can be provided.

DESCRIPTION OF DRAWINGS

FIG. 1 is a first perspective view showing a robot gripper according toone embodiment of the present invention.

FIG. 2 is a second perspective view showing the robot gripper accordingto one embodiment of the present invention.

FIG. 3 is a front view of FIG. 2 .

FIG. 4 is a side view of FIG. 2 .

FIG. 5 is a comparative view showing comparison of disassembled andassembled shapes of the robot gripper according to one embodiment of thepresent invention.

FIG. 6 is a reference view for describing a pinch grip operation of therobot gripper according to one embodiment of the present invention.

FIGS. 7 and 8 show simulation results for a vector direction of a forceapplied to a fingertip, which is determined according to a length ofeach of links that constitute a four-bar link device, in the robotgripper according to one embodiment of the present invention.

FIGS. 9 to 11 are dynamic simulation images of the robot gripperaccording to one embodiment of the present invention.

FIG. 12 is a flowchart showing a method of operating a robot gripperaccording to one embodiment of the present invention.

FIG. 13 is a reference view showing a step S121 of FIG. 12 .

FIG. 14 is a reference view showing a step S122 of FIG. 12 .

FIG. 15 is a reference view showing a step S123 of FIG. 12 .

FIG. 16 is a reference view showing a step S124 of FIG. 12 .

FIG. 17 is a reference view showing a step S125 of FIG. 12 .

MODE FOR INVENTION

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.However, the technical idea of the present invention is not limited tothe embodiments described herein, but may be realized in differentforms. The embodiments introduced herein are provided to sufficientlydeliver the idea of the present invention to those skilled in the art sothat the disclosed contents may become thorough and complete.

When it is mentioned in the present disclosure that one element is onanother element, it means that one element may be directly formed onanother element, or a third element may be interposed between oneelement and another element. Further, in the drawings, thicknesses offilms and areas are exaggerated for efficient description of thetechnical contents.

In addition, in the various embodiments of the present disclosure, theterms such as first, second, and third are used to describe variouselements, but the elements are not limited to the terms. The terms areused only to distinguish one element from another element. Therefore, anelement mentioned as a first element in one embodiment may be mentionedas a second element in another embodiment. The embodiments described andillustrated herein include their complementary embodiments. Further, theterm “and/or” used herein is used to include at least one of theelements enumerated before and after the term.

As used herein, the terms of a singular form may include plural formsunless the context clearly indicates otherwise. Further, the terms suchas “including” and “having” are used to designate the presence offeatures, numbers, steps, elements, or combinations thereof described inthe present disclosure, and shall not be construed to preclude anypossibility of the presence or addition of one or more other features,numbers, steps, elements, or combinations thereof.

Further, in the following description of the present invention, detaileddescriptions of known functions and configurations incorporated hereinwill be omitted when they may make the subject matter of the presentinvention unnecessarily unclear.

FIGS. 1 to 11 are views for describing a robot gripper according to oneembodiment of the present invention.

As shown in FIGS. 1 to 5 , according to one embodiment of the presentinvention, a robot gripper 10 may include a finger unit 100, a fingertip200, and a driving unit 300.

The finger unit 100 may be provided upward from an edge of a top surfaceof a housing 301 of the driving unit 300 by using the top surface of thehousing 301 of the driving unit 300 as a palm surface. At least twofinger units 100 may be provided to grasp an object. According to oneembodiment of the present invention, the at least two finger units 100may be underactuated by the driving unit 300, which will be described inmore detail below. In addition, for convenience of description, it willbe assumed in the following description that a pair of finger units 100are provided.

The pair of finger units 100 may symmetrically face each other. Thefingertip 200 serving as a tip of a finger may be provided at a terminalend of each of the pair of finger units 100.

According to one embodiment of the present invention, the finger unit100 may implement pinch grip of the fingertip 200 with respect to theobject, and may have a four-bar link device 110 to grasp the object. Inaddition, the finger unit 100 may include a connection link 120.

The four-bar link device 110 may include an input link 111, an outputlink 112, an intermediate link 113, and a frame link 114.

The input link 111 may be connected to the driving unit 300 to rotate bya rotation torque transmitted from the driving unit 300. The input link111 may have a bar shape. In this case, one longitudinal end of theinput link 111 may be connected to the driving unit 300, and an oppositelongitudinal end of the input link 111 may be connected to theintermediate link 113.

The output link 112 may face the input link 111. The output link 112 mayhave a bar shape. The output link 112 may be connected to the connectionlink 120, the intermediate link 113, and the frame link 114. In detail,one longitudinal end of the output link 112 may be connected to theconnection link 120 and the frame link 114, and an opposite longitudinalend of the output link 112 may be connected to the intermediate link113.

The intermediate link 113 may have a bar shape. The intermediate link113 may be connected between the input link 111 and the output link 112.In detail, one intermediate end of the intermediate link 113 may bejoint-coupled to the opposite longitudinal end of the input link 111. Inaddition, an opposite longitudinal end of the intermediate link 113 maybe joint-coupled to the opposite longitudinal end of the output link112.

The frame link 114 may have a bar shape. The frame link 114 may becoupled between the output link 112 and the input link 111. In detail,one longitudinal end of the frame link 114 may be joint-coupled to theone longitudinal end of the output link 112. In addition, an oppositelongitudinal end of the frame link 114 may be joint-coupled to the onelongitudinal end of the input link 111. According to an embodiment ofthe present invention, the frame link 114 may be defined as a first barof the finger unit 100.

According to one embodiment of the present invention, a vector directionof a force applied to the fingertip 200 that implements various pinchgrip operations may be determined according to a length relation oflinks that constitute sides of the four-bar link device 110,respectively, that is, according to a length relation of the input link111, the output link 112, the intermediate link 113, and the frame link114, which will be described in more detail below.

Meanwhile, the connection link 120 may connect the four-bar link device110 to the fingertip 200. The connection link 120 may have a bar shape.One longitudinal end of the connection link 120 may be connected to theone longitudinal end of the output link 112. In addition, an oppositelongitudinal end of the connection link 120 may be connected to thefingertip 200. According to one embodiment of the present invention, theconnection link 120 may be defined as a second bar of the finger unit100.

According to one embodiment of the present invention, the finger unit100 may further include a parallelogrammic link device 130. Theparallelogrammic link device 130 may be coupled to the four-bar linkdevice 110 and the connection link 120. Accordingly, theparallelogrammic link device 130 may maintain an installation angle ofthe fingertip 200. In this case, the parallelogrammic link device 130may not operate independently. The parallelogrammic link device 130 maybe dependent on an operation of the four-bar link device 110 connectedto the driving unit 300.

Referring to FIG. 5 , the parallelogrammic link device 130 may include afirst link 131, a second link 132, a third link 133, a fourth link 134,and a fifth link 135.

The first link 131 may have a bar shape. One longitudinal end of thefirst link 131 may be connected to the housing 301 of the driving unit300. In addition, an opposite longitudinal end of the first link 131 maybe connected to the second link 132.

The second link 132 may have a bar shape. One longitudinal end of thesecond link 132 may be joint-coupled to the opposite longitudinal end ofthe first link 131. In addition, an opposite longitudinal end of thesecond link 132 may be connected to the fourth link 134.

The third link 133 may have a bar shape. One longitudinal end of thethird link 133 may be connected to a shaft at which the longitudinalends of the connection link 120 and the output link 112 are connectedand joint-coupled to each other. In addition, an opposite longitudinalend of the third link 133 may be connected to a shaft at which the firstlink 131 and the second link 132 are joint-coupled to each other. Inthis case, the third link 133 may form a V-shape with the second link132 to increase a radius of rotation. In this case, the third link 133may be formed integrally with the second link 132.

The fourth link 134 may have a bar shape. One longitudinal end of thefourth link 134 may be joint-coupled to the opposite longitudinal end ofthe second link 132. In addition, an opposite longitudinal end of thefourth link 134 may be connected to the fifth link 135.

The fifth link 135 may have a bar shape. One longitudinal end of thefifth link 135 may be joint-coupled to the opposite longitudinal end ofthe fourth link 134. In addition, an opposite longitudinal end of thefifth link 135 may be connected to the fingertip 200.

Meanwhile, as shown in FIG. 6 , according to one embodiment of thepresent invention, the finger unit 100 may further include a stopper140. The stopper 140 may be provided between the output link 112 and theframe link 114. The stopper 140 may restrain a rotation of the outputlink 112 in a direction of increasing an angle formed between the outputlink 112 and the frame link 114.

In addition, referring to FIG. 6 , according to one embodiment of thepresent invention, the finger unit 100 may further include an elasticmember 150. The elastic member 150 may be provided between the outputlink 112 and the frame link 114. The elastic member 150 may beelastically deformed in a case where an inclination of the output link112 is changed to increase the angle formed between the output link 112and the frame link 114 when the driving unit 300 is driven. Accordingly,adaptive grasp of the robot gripper 10 may be enabled. In addition, theelastic member 150 may recover the inclination of the output link 112into an initial state through an elastic restoring force so that theangle formed between the output link 112 and the frame link 114 may forman initially set angle again when the driving unit 300 is not driven.

The elastic member 150 may be configured as a spring, preferably as atorsion spring.

When the elastic member 150 is configured as a torsion spring, a torsiontorque may be generated when the inclination of the output link 112 ischanged, and the torsion torque may act as a restoring force forrecovering the inclination of the output link 112 into the initialstate.

Referring again to FIGS. 1 to 5 , the fingertip 200 may be provided atthe terminal end of the finger unit 100 to interwork with an operationof the finger unit 100. In detail, one longitudinal end of the fingertip200 may be connected to the opposite longitudinal end of the fifth link135 of the parallelogrammic link device 130. In this case, the onelongitudinal end of the fingertip 200 and the opposite longitudinal endof the fifth link 135 may be connected to the opposite longitudinal endof the connection link 120. The fingertip 200 may have a contact surfacecapable of pinch-gripping the object, and the fingertips 200 provided atthe terminal ends of the finger units 100 facing each other may havecontact surfaces facing each other. In this case, the contact surface ofthe fingertip 200 may be set to form a perpendicular surface that isperpendicular to the top surface of the housing 301 of the driving unit300, and a set state may be maintained to be fixed by theparallelogrammic link device 130.

According to one embodiment of the present invention, when the fingerunit 100 is operated, the fingertip 200 may pinch-grip the object bymoving toward an inner area, which is formed as the pair of finger units100 face each other, while adapting to a conflict with a constraint ofan external environment.

In this case, a force applied to the fingertip 200 to enable the pinchgrip with respect to the object may act in a direction of raising theobject upward while acting toward the inner area formed as the pair offinger units 100 face each other. In addition, the force applied to thefingertip 200 to enable the pinch grip with respect to the object mayact in a direction of lowering the object downward while acting towardthe inner area formed as the pair of finger units 100 face each other.

In this case, as described above, the vector direction of the forceapplied to the fingertip 200 may be determined according to the lengthrelation of the links that constitute the sides of the four-bar linkdevice 110, respectively, that is, according to the length relation ofthe input link 111, the output link 112, the intermediate link 113, andthe frame link 114.

Referring to FIG. 6 , as an input torque τ₀ is transmitted from thedriving unit 300 to the input link 111, the input link 111 may rotateabout a position {O}. In this case, the fingertip 200 making contactwith an arbitrary surface may exert an output force f_(E) onto thearbitrary surface, and a vector direction θ_(f) of the force applied tothe fingertip 200 may be determined according to the length relation ofthe links 111, 112, 113, and 114. When passing through a tangent angleψ_(E) at a contact point of the surface, a sliding direction of thefingertip 200 may be found by using a normal angle

$\psi_{\frac{1}{E}}$

that is perpendicular to the surface. For example, when assuming thatthe fingertip 200 makes contact with a surface having a tangent anglewithin _, a normal angle of the surface may be. Such surface angles maybe frequently observed in our daily life, and may be the most commonangles. When _ on the surface, the fingertip 200 may not move anywhere.When _, the fingertip 200 may slide in a direction toward an innerportion that is formed as the finger units 100 face each other. When _,the fingertip 200 may slide in a direction toward an outer portion.

As described above, according to one embodiment of the presentinvention, the vector direction of the force applied to the fingertip200 may be determined according to the length relation of the links thatconstitute the sides of the four-bar link device 110, respectively. Inthis case, the length relation of the input link 111, the intermediatelink 113, and the output link 112, which are the links that constitutethe sides of the four-bar link device 110, respectively, may becalculated as follows. In this case, a length of the frame link 114 maybe automatically set when lengths of the input link 111, theintermediate link 113, and the output link 112 are calculated.

The length relation of the input link 111, the intermediate link 113,and the output link 112 may be defined according to vector directions offorces generated when the opposite longitudinal end of the connectionlink 120 makes contact with any three points on a horizontal plane. Theopposite longitudinal end of the connection link 120 may substantiallyrefer to the fingertip 200.

For example, when a vector direction of the force acting on the oppositelongitudinal end of the connection link 120 is −20° in a case where theopposite longitudinal end of the connection link 120 makes contact withan −100 mm point on the horizontal plane, a vector direction of theforce acting on the opposite longitudinal end of the connection link 120is −55° in a case where the opposite longitudinal end of the connectionlink 120 makes contact with a −75 mm point on the horizontal plane, avector direction of the force acting on the opposite longitudinal end ofthe connection link 120 is −90° in a case where the oppositelongitudinal end of the connection link 120 makes contact with a −50 mmpoint on the horizontal plane, and an angle formed between the outputlink 112 and the connection link 120 is set to 125.5°, the length of theinput link 111 may be calculated as 27.77 mm, the length of theintermediate link may be calculated as 48.02 mm, and the length of theoutput link may be calculated as 20.72 mm.

In addition, when a vector direction of the force acting on the oppositelongitudinal end of the connection link 120 is −90° in a case where theopposite longitudinal end of the connection link 120 makes contact witha −100 mm point on the horizontal plane, a vector direction of the forceacting on the opposite longitudinal end of the connection link 120 is−110° in a case where the opposite longitudinal end of the connectionlink 120 makes contact with a −90 mm point on the horizontal plane, avector direction of the force acting on the opposite longitudinal end ofthe connection link 120 is −120° in case where the opposite longitudinalend of the connection link 120 makes contact with a −80 mm point on thehorizontal plane, and an angle formed between the output link 112 andthe connection link 120 is set to 69°, the length of the input link 111may be calculated as 27.77 mm, the length of the intermediate link maybe calculated as 48.02 mm, and the length of the output link may becalculated as 20.72 mm.

As described above, based on the defined length relation of the links, aforce acting in the direction of raising the object upward while actingtoward the inner area, which is formed as the pair of finger units 100face each other, may be applied to the fingertip 200, or a force actingin the direction of lowering the object downward while acting toward theinner area, which is formed as the pair of finger units 100 face eachother, may be applied to the fingertip 200.

In other words, referring to a simulation result of FIG. 7 , while theoutput link 112 has a relatively shorter length than the input link 111and the intermediate link 113, when the input link 111 has a relativelyshorter length than the intermediate link 113, the force applied to thefingertip 200 may act in the direction of raising the object upwardwhile acting toward the inner area, which is formed as the pair offinger units 100 face each other.

In addition, referring to a simulation result of FIG. 8 , while theoutput link 112 has a relatively shorter length than the input link 111and the intermediate link 113, when the input link 111 has a relativelylonger length than the intermediate link 113, the force applied to thefingertip 200 may act in the direction of lowering the object downwardwhile acting toward the inner area, which is formed as the pair offinger units 100 face each other.

In this case, an angle formed between the connection link 120 and theoutput link 112, which is set when the force applied to the fingertip200 acts in the direction of raising the object upward while actingtoward the inner area that is formed as the pair of finger units 100face each other, may be relatively greater than an angle formed betweenthe connection link 120 and the output link 112, which is set when theforce applied to the fingertip 200 acts in the direction of lowering theobject downward while acting toward the inner area that is formed as thepair of finger units 100 face each other.

FIGS. 9 to 11 are dynamic simulation images of the robot gripperaccording to one embodiment of the present invention. First, referringto FIG. 9 , it may be found that the fingertip 200 slidably moves inwardof the robot gripper 10 even when making contact with the plane. Inaddition, referring to FIG. 10 , it may be found that the fingertip 200slidably moves inward of the robot gripper 10 and raises a small objectwhile pinching the small object when making contact with the plane.Further, referring to FIG. 11 , it may be found that the robot gripper10 adaptively grasps an indeterminate-shape object.

Referring again to FIGS. 1 to 5 , the driving unit 300 may be connectedto the pair of finger units 100. According to one embodiment of thepresent invention, two finger units 100 may be driven by one drivingunit 300. In other words, the two finger units 100 may be underactuatedby the one driving unit 300. In addition, the driving unit 300 mayprovide a base part that serves as a palm for the finger unit 100 thatserves as a finger.

According to one embodiment of the present invention, the driving unit300 may include an actuator for driving the input links 111 of thefinger units 100 facing each other on both sides of the driving unit300. In this case, the driving unit 300 may include the housing 301 forproviding a mounting space for the actuator. The housing 301 may beprovided in a form of a palm or a wrist. The housing 301 may act as thebase part for the finger unit 100.

According to one embodiment of the present invention, the actuator fordriving the input links 111 on the both sides may include a worm gear320 and a worm wheel 330. In this case, the actuator may receive a powerfrom the motor 310.

In this case, the motor 310 may be disposed on an upper side of a spacethat is set inside the housing 301 (based on the drawings). The motor310 may be connected to the worm gear 320, and driven to rotate the wormgear 320 when an electric power is applied.

The worm gear 320 may be disposed on a lower side of the space that isset inside the housing 301 (based on the drawings). The worm gear 320may be connected to the motor 310. The worm gear 320 may be connected tothe motor 310 in a vertical direction. The worm gear 320 may be rotatedby the motor 310. In this case, since the worm gear 320 may not rotatein a reverse direction, a self-locking transmission mechanism may beimplemented through the worm gear 320. As a result, when the electricpower is not applied, malfunction of the finger unit 100 may beprevented to ensure safety.

The worm wheel 330 may be disposed on the lower side of the space thatis set inside the housing 301. The worm wheel 330 may be engaged withthe worm gear 320 so as to be rotated. The worm wheel 330 may beprovided in a number corresponding to the finger unit 100, morespecifically, the input link 111. Accordingly, one input link 111 may berotatably and axially coupled to each worm wheel 330.

Hereinafter, a method of operating a robot gripper according to oneembodiment of the present invention will be described with reference toFIGS. 12 to 17 . In this case, reference numerals for detailedcomponents of the robot gripper will be described with reference toFIGS. 1 to 6 .

Referring to FIG. 12 , according to one embodiment of the presentinvention, a method of operating a robot gripper may include a four-barlink device operation step S110 and a fingertip pinch grip step S120.

First, the four-bar link device operation step S110 may be a step ofoperating a four-bar link device 110 to perform pinch grip of afingertip 200. In the four-bar link device operation step S110, anelectric power may be applied to a driving unit 300, more specifically,a motor 310 so as to drive an actuator including a worm gear 320 and aworm wheel 330. The four-bar link device 110 may be operated by theactuator driven as described above.

Next, the pinch grip step S120 may be a step of allowing the fingertip200 to pinch-grip an object placed in various environments by theoperated four-bar link device 110. The pinch grip step S120 may bedivided into an inclined surface ascending/descending operation S121, anouter wall climbing operation S122, an adaptive grasp operation S123, apeg-in-hole operation S124, and a downward pushing operation S125 basedon the fingertip 200.

Referring to FIG. 13 , when the object is placed on various inclinedsurfaces, the fingertip 200 may perform the inclined surfaceascending/descending operation S121. First, the fingertip 200 located ona left side based on the drawing may move in a direction A toward aninner area, which is formed as the pair of finger units 100 face eachother, to perform the pinch grip on the object (1), may ascend aninclined surface located on a lower side of a position in which theobject is placed while conforming to environmental constraints whencolliding with the inclined surface (2), and may continue to move in thedirection A to eventually make contact with the object located on amovement path (3). In addition, the fingertip 200 located on a rightside based on the drawing may move in a direction A toward the innerarea, which is formed as the pair of finger units 100 face each other,to perform the pinch grip on the object (1), may descend an inclinedsurface located on an upper side of the position in which the object isplaced while conforming to environmental constraints when colliding withthe inclined surface (2), and may continue to move in the direction A toeventually make contact with the object located on a movement path (3).

As described above, according to the robot gripper 10 of one embodimentof the present invention, the fingertips 200 on both sides may makecontact with both sides of the object through the inclined surfaceascending/descending operation S121 so as to pinch-grip the object.

Referring to FIG. 14 , when the object is placed on a surface having oneside configured as an outer wall, the fingertip 200 may perform theouter wall climbing operation S122. First, the fingertip 200 located ona left side based on the drawing may move in a direction A toward theinner area, which is formed as the pair of finger units 100 face eachother, to perform the pinch grip on the object (1), may move whileconforming to environmental constraints when colliding with a surfacelocated on a left side of the position in which the object is placed(2), and may eventually make contact with the object located on amovement path (3).

In addition, the fingertip 200 located on a right side based on thedrawing may move in a direction A toward the inner area, which is formedas the pair of finger units 100 face each other, to perform the pinchgrip on the object (1), may move in a direction C, which is a directionof raising the object, while conforming to environmental constraints toclimb an outer wall located on a lower side of the position in which theobject is placed when first colliding with the outer wall (2), and maymove in the direction A again after the climbing to eventually makecontact with the object located on a movement path (3). In this case,when an outer wall is also present on a left side of a surface on whichthe object is placed, the fingertip 200 located on the left side may beoperated in the same manner as the outer wall climbing operation S122 ofthe fingertip 200 on the right side.

As described above, according to the robot gripper 10 of one embodimentof the present invention, the fingertips 200 on one or both sides maymake contact with the both sides of the object through the outer wallclimbing operation S122 so as to pinch-grip the object.

Referring to FIG. 15 , when the object has an indeterminate shape, thefinger unit 100 may perform the adaptive grasp operation S123. Thefinger units 100 on the both sides may move in a direction A toward theinner area, which is formed as the finger units 100 on the both sidesface each other, to grasp the object having the indeterminate shape. Inthis case, when a first bar of the finger unit 100 first make contactwith a surface of the object having the indeterminate shape, theconnection link 120 acting as a second bar of the finger unit 100 andthe fingertip 200 acting as a third bar of the finger unit 100 maycontinue to move in the direction A to eventually make contact with thesurface of the object placed on a movement path.

As described above, according to the robot gripper 10 of one embodimentof the present invention, the finger units 100 on the both sides maymake contact with the object having the indeterminate shape through theadaptive grasp operation S123 so as to grasp the object.

Referring to FIG. 16 , when the object inserted in one hole is moved soas to be inserted into a next hole, the fingertip 200 may perform thepeg-in-hole operation S124. First, the fingertips 200 on the both sidesmay move in a direction A in which the fingertips 200 face each other topinch-grip the object (1). Then, the fingertips 200 on the both sidesmay move in a direction B, which is a direction of raising thepinch-gripped object, to raise the object so as to pull out the objectfrom the one hole (2).

Next, when the robot gripper 10 is moved so as to be placed on the nexthole (3), the fingertip 200 may move in a direction C, which is adirection of pushing the pinch-gripped object downward, to push theobject downward so as to insert the object into the next hole (4).

As described above, according to the robot gripper 10 of one embodimentof the present invention, the fingertips 200 on the both sides may movethe object inserted in one hole to insert the object into the next holethrough the peg-in-hole operation S124.

Referring to FIG. 17 , when the object placed on a surface having aspecific height is moved onto a surface having a height that is lowerthan the specific height, the fingertip 200 may perform the downwardpushing operation S125. First, the fingertips 200 on the both sides maymove in a direction A, which is a direction in which the fingertips 200face each other, to pinch-grip the object.

Next, when the robot gripper 10 is moved so as to be placed on thesurface having a lower position than an initial position (3), thefingertip 200 may move in a direction C, which is a direction of pushingthe pinch-gripped object downward, to push the object downward so as tomove the object onto the surface having the lower position than theinitial position.

As described above, according to the robot gripper 10 of one embodimentof the present invention, the fingertips 200 on the both sides may movethe object to the lower position than the initial position through thedownward pushing operation S125.

Although the exemplary embodiments of the present invention have beendescribed in detail, the scope of the present invention is not limitedto a specific embodiment, and should be interpreted by the appendedclaims. In addition, it should be understood by those of ordinary skillin the art that various changes and modifications can be made withoutdeparting from the scope of the present invention.

1. A robot gripper comprising: at least two finger units symmetricallyfacing each other; a fingertip provided at a terminal end of the fingerunit, and interworking with an operation of the finger unit; and adriving unit connected to the finger unit to operate the finger unit,wherein, when the finger unit is operated, the fingertip pinch-grips anobject by moving toward an inner area, which is formed as the at leasttwo finger units face each other, while adapting to a conflict with aconstraint of an external environment, and a force applied to thefingertip to enable the pinch grip acts in a direction of raising theobject upward while acting toward the inner area, or acts in a directionof lowering the object downward while acting toward the inner area. 2.The robot gripper of claim 1, wherein the finger unit includes afour-bar link device, and a vector direction of the force applied to thefingertip is determined according to a length relation of links thatconstitute sides of the four-bar link device, respectively.
 3. The robotgripper of claim 2, wherein the finger unit further includes aconnection link, the connection link connects the four-bar link deviceto the fingertip, and the four-bar link device includes: an input linkhaving one longitudinal end connected to the driving unit; an outputlink facing the input link, and having one longitudinal end connected toone longitudinal end of the connection link; an intermediate linkconnected between an opposite longitudinal end of the input link and anopposite longitudinal end of the output link; and a frame link connectedbetween the one longitudinal end of the output link and the onelongitudinal end of the input link.
 4. The robot gripper of claim 3,wherein a length relation of the input link, the intermediate link, andthe output link is defined according to vector directions of forcesgenerated when an opposite longitudinal end of the connection link makescontact with any three points on a horizontal plane, and, based on thedefined length relation, a force acting in the direction of raising theobject upward while acting toward the inner area is applied to thefingertip, or a force acting in the direction of lowering the objectdownward while acting toward the inner area is applied to the fingertip.5. The robot gripper of claim 4, wherein, while the output link has arelatively shorter length than the input link and the intermediate link,when the input link has a relatively shorter length than theintermediate link, the force applied to the fingertip acts in thedirection of raising the object upward while acting toward the innerarea.
 6. The robot gripper of claim 5, wherein, while the output linkhas a relatively shorter length than the input link and the intermediatelink, when the input link has a relatively longer length than theintermediate link, the force applied to the fingertip acts in thedirection of lowering the object downward while acting toward the innerarea.
 7. The robot gripper of claim 6, wherein an angle formed betweenthe connection link and the output link, which is set when the forceapplied to the fingertip acts in the direction of raising the objectupward while acting toward the inner area, is relatively greater than anangle formed between the connection link and the output link, which isset when the force applied to the fingertip acts in the direction oflowering the object downward while acting toward the inner area.
 8. Therobot gripper of claim 3, wherein the finger unit further includes aparallelogrammic link device, and the parallelogrammic link device iscoupled to the four-bar link device and the connection link to maintainan installation angle of the fingertip, and is dependent on an operationof the four-bar link device.
 9. The robot gripper of claim 3, whereinthe finger unit further includes a stopper, and the stopper is formedbetween the output link and the frame link, and configured to restrain arotation of the output link in a direction of increasing an angle formedbetween the output link and the frame link.
 10. The robot gripper ofclaim 3, wherein the finger unit further includes an elastic member, andthe elastic member is formed between the output link and the frame link,elastically deformed in a case where an inclination of the output linkis changed to increase an angle formed between the output link and theframe link when the driving unit is driven, and configured to recoverthe inclination of the output link into an initial state through anelastic restoring force so that the angle formed between the output linkand the frame link forms an initially set angle again when the drivingunit is not driven.
 11. The robot gripper of claim 1, wherein the atleast two finger units are underactuated by the driving unit.
 12. Therobot gripper of claim 11, wherein the driving unit includes: one motor;one worm gear rotated by the one motor; and worm wheels provided in anumber corresponding to the at least two finger units so as to beconnected to the at least two finger units, respectively, and engagedwith the one worm gear so as to be rotated.